From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753394Ab3AYIKE (ORCPT ); Fri, 25 Jan 2013 03:10:04 -0500 Received: from szxga01-in.huawei.com ([119.145.14.64]:45035 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751275Ab3AYIKD (ORCPT ); Fri, 25 Jan 2013 03:10:03 -0500 Message-ID: <51023D61.9000901@huawei.com> Date: Fri, 25 Jan 2013 16:08:01 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130107 Thunderbird/17.0.2 MIME-Version: 1.0 To: Tejun Heo CC: Al Viro , David Rientjes , LKML , Cgroups Subject: [PATCH v2] cpuset: fix cpuset_print_task_mems_allowed() vs rename() race Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org rename() will change dentry->d_name. The result of this race can be worse than seeing partially rewritten name, but we might access a stale pointer because rename() will re-allocate memory to hold a longer name. It's safe in the protection of dentry->d_lock. v2: check NULL dentry before acquiring dentry lock. Signed-off-by: Li Zefan --- kernel/cpuset.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 16be7c9..4f9dfe4 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -2606,8 +2606,16 @@ void cpuset_print_task_mems_allowed(struct task_struct *tsk) dentry = task_cs(tsk)->css.cgroup->dentry; spin_lock(&cpuset_buffer_lock); - snprintf(cpuset_name, CPUSET_NAME_LEN, - dentry ? (const char *)dentry->d_name.name : "/"); + + if (!dentry) { + strcpy(cpuset_name, "/"); + } else { + spin_lock(&dentry->d_lock); + strlcpy(cpuset_name, (const char *)dentry->d_name.name, + CPUSET_NAME_LEN); + spin_unlock(&dentry->d_lock); + } + nodelist_scnprintf(cpuset_nodelist, CPUSET_NODELIST_LEN, tsk->mems_allowed); printk(KERN_INFO "%s cpuset=%s mems_allowed=%s\n", -- 1.8.0.2